The death toll from recent "extreme weather events" has been sharply declining since the 1920s, as my valued colleague Indur Goklany has valorously pointed out. Air conditioning, flood control, earthquake proofing and better weather forecasting have all helped. Despite vast media coverage, extreme weather now causes only a half-percent of global deaths. A large part of the gains came through crop production increases using fossil-fueled industrial fertilizers and irrigation pumps. This meant the world had fossil-fueled food to share with countries suddenly caught by devastating (but short- term) drought or flood.

But Indur neglected one aspect of extreme weather events—the "little ice ages." They are the flip side of the 1500-year warming cycle. The last one began in 1300 AD and ended in 1850, recent enough that many of our great-grandparents had to cope. We don't know when the next one will come, perhaps not for another 300 years—but when it does, "Look out!"

As an example, civilizations collapsed around the world, simultaneously, 4200 years ago—in southern Green, Palestine, Egypt, Iraq, Pakistan, and China. The nomads on the Asian steppes gave up their seasonal farming, put their huts on wheels, and simply followed their herds seeking ever-scarcer grass. This massive drought—driven by a "little ice age"— lasted 300 years!

Egypt had more food security through its early history than anyplace else, but it collapsed in famine and political chaos three times between 4200 and 1000 BC—all of them during "little ice ages." The Nile floods were also far below normal during the cold Dark Ages (450-950 AD) and during our recent Little Ice Age.

How many people would starve if agriculture failed again, suddenly and simultaneously in Greece, Palestine, Egypt, India, and China—for 300 years? What future Huns would come knocking on the city gates? Would plague-infected rats again move in?

The "little ice age" climates are inherently less stable and more violent than the warming intervals. The Netherlands was hit by massive sea floods three times in 50 years as the Little Ice Age began. Each of these floods drowned more than 100,000 people. Will the Dutch levees hold in the next "little ice age"? What about New Orleans in a far less stable climate?

As we today enjoy the stable weather of a sunlit interglacial global warming, we had best not forget the massive disasters during the cold phases of the Dansgaard-Oeschger cycle. In the last 160 years, we have not only become, used to the piddling "disasters" of a global warming phase, but smug that we have been able to rescue small countries with our technology. Fossil fuels have competently carried food aid to famine victims during small, short famines. But, in a future Little Ice Age, the summers will cloudy, cold, interrupted by early frosts and hailstorms—for several hundred years.

We invented high-yield farming at the end of the Little Ice Age, to reduce the death toll from the persistent crop failures. But the world's population since 1850 has risen from perhaps 1 billion to 6.6 billion, and may rise by 2 billion more before it peaks about 2050. Where would we move the at-risk populations?

Global vegetation has sharply increased with today's additional sunshine and favorable rain patterns—plus the added plant fertilization due to more CO2 in the atmosphere. What if the climate turns suddenly cold and unstable and the oceans suck more of the CO2 out of the atmosphere?

We should take full advantage of the favorable climate we have been granted to increase research on high-yield agriculture, biotechnology, water conservation and other advances now only dreamt of. We must make true improvements in energy technology (not erratic windmills and solar panels that will be even less effective in a cloudy little ice age than today).The greatest danger to the future population is to be unaware that the good period will not last.

For a million years, humans have been using the warming periods to advance civilization. We are comfortable, well fed, and not competing for caves because those who came before us advanced human society each time the climate provided a few hundred years of safety. Should we do any less for those who will come after us?

Dennis T. Avery is an environmental economist, and a senior fellow for the Hudson Institute in Washington, DC. He was formerly a senior analyst for the Department of State. He is co-author, with S. Fred Singer, of Unstoppable Global Warming Every 1500 Hundred Years, Readers may write him at PO Box 202, Churchville, VA 24421 or email to cgfi@hughes.net